Method of measuring motion

ABSTRACT

A method for measuring motion of a user, which is adapted to apply to output signals proportional to rotation and translational motion of the carrier, respectively from angular rate sensors and acceleration sensors, is more suitable for emerging MEMS angular rate and acceleration sensors. Compared with a conventional IMU, said processing method utilizes a feedforward open-loop signal processing scheme to obtain highly accurate motion measurements by means of signal digitizing, temperature control, sensor error and misalignment calibrations, attitude updating, and damping control loops, and dramatically shrinks said size of mechanical and electronic hardware and power consumption, meanwhile, obtains highly accurate motion measurements.

CROSS REFERENCE OF RELATED APPLICATION

[0001] This is a regular application of a provisional application havingan application number of No. 60/206,992 and a filing date of May 24,2000.

BACKGROUND OF THE PRESENT INVENTION

[0002] 1. Field of the Present Invention

[0003] The present invention relates to a method for measuring motion ofa user, and more particularly to a method for a inertial measurementunit process for measuring motion of a vehicle, wherein output signalsof an angular rate producer and acceleration producer, including anangular rate device array and an acceleration device array, or anangular rate and acceleration simulator, are processed to obtain highlyaccurate attitude and heading measurements of a carrier under dynamicenvironments, and thermal control processing steps are incorporated tostabilize and optimize the performance of motion measurements.

[0004] 2. Description of Related Arts

[0005] Generally, conventional methods for determining the motion of acarrier are to employ inertial angular rate devices and accelerationdevices, such as gyros and accelerometers, radio positioning systems,and hybrid systems.

[0006] In principle, inertial motion measurement methods depend on threeorthogonally mounted inertial rate sensors and three orthogonallymounted accelerometers to obtain three-axis rate and accelerationmeasurement signals. The three orthogonally mounted inertial ratesensors and three orthogonally mounted accelerometers with additionalsupporting mechanical structure and electronics devices areconventionally called an Inertial Measurement Unit (IMU). The existingIMUs may be cataloged into Platform IMU and Strapdown IMU.

[0007] In the Platform IMU, rate sensor and accelerometers are installedon a stabilized platform. Attitude measurements can be directly pickedoff from the platform structure. But attitude rate measurements can notbe directly obtained from the platform. Moreover, there are highlyaccurate feedback controlling loops associated with the platform.

[0008] Compared with the platform IMU, in the strapdown IMU, ratesensors and accelerometers are directly fixed in the carrier and movewith the carrier. The output signals of strapdown rate sensors andaccelerometers are expressed in the carrier body frame. The attitude andattitude rate measurements can be obtained by means of a series ofcomputations.

[0009] Conventional inertial rate sensors include Floated IntegratingGyros (FIG), Dynamically Tuned Gyros (DTG), Ring Laser Gyros (RLG),Fiber-Optic Gyros (FOG), Electrostatic Gyros (ESG), Josephson JunctionGyros (JJG), Hemisperical Resonating Gyros (HRG), etc.

[0010] Conventional accelerometer includes Pulsed Integrating PendulousAccelerometer (PIPA), Pendulous Integrating Gyro Accelerometer (PIGA),etc.

[0011] The processing methods in conventional IMUs vary with types ofgyros and accelerometers used in the IMUs. Because conventional gyrosand accelerometers have big size, large power consumption, and movingmass, complex feedback controlling loops are required to obtain stablemotion measurements. For example, dynamic-tuned gyros and accelerometersneed force-rebalance loops to create a moving mass idle position. Thereare often pulse modulation force-rebalance circuits associated withdynamic-tuned gyros and accelerometer based IMUs.

[0012] New horizons are opening up for inertial sensor devicetechnologies. MEMS (MicroElectronicMechanicalSystem) inertial sensorsoffer tremendous cost, size, reliability improvements for guidance,navigation, and control systems, compared with conventional inertialsensors. It is well-known that the silicon revolution began over threedecades ago, with the introduction of the first integrated circuit. Theintegrated circuit has changed virtually every aspect of our lives. Thehallmark of the integrated circuit industry over the past three decadeshas been the exponential increase in the number of transistorsincorporated onto a single piece of silicon. This rapid advance in thenumber of transistors per chip leads to integrated circuits withcontinuously increasing capability and performance. As time hasprogressed, large, expensive, complex systems have been replaced bysmall, high performance, inexpensive integrated circuits. While thegrowth in the functionality, of microelectronic circuits has been trulyphenomenal, for the most part, this growth has been limited to theprocessing power of the chip.

[0013] MEMS, or, as stated more simply, micromachines, are consideredthe next logical step in the silicon revolution. It is believed thatthis coming step will be different, and more important than simplypacking more transistors onto silicon. The hallmark of the next thirtyyears of the silicon revolution will be the incorporation of new typesof functionality onto the chip structures, which will enable the chipto, not only think, but to sense, act, and communicate as well.

[0014] Prolific MEMS angular rate sensor approaches have been developedto meet the need for inexpensive yet reliable angular rate sensors infields ranging from automotive to consumer electronics. Single inputaxis MEMS angular rate sensors are based on either translationalresonance, such as tuning forks, or structural mode resonance, such asvibrating rings. Moreover, Dual Input Axis MEMS Angular Rate Sensors maybe based on angular resonance of a rotating rigid rotor suspended bytorsional springs. The inherent symmetry of the circular design allowsangular rate measurement about two axes simultaneously. Preferred MEMSangular rate sensors are mostly based on an electronically-driven tuningfork method. Such MEMS gyros operate in accordance with the dynamictheory (Coriolis Effect) that when an angular rate is applied to atranslating body, a Coriolis force is generated. When this angular rateis applied, the axis of an oscillating tuning fork, its tines receive aCoriolis force, which then produces torsional forces about the sensoraxis. These forces are proportional to the applied angular rate, whichthen can be measured capacitively, as shown in FIG. 16.

[0015] MEMS devices can be fabricated by bulk micromachining (chemicaletching) single crystal silicon or by surface micromachining layers ofploysilicon. Surface micromachined devices are typically a few micronsto 10 microns thick while bulk machining produces devices 100 to 500microns thick. Angular rate sensors created with surface machining havevery low masses and are presently not sensitive enough for militaryapplications but are useful for automotive applications. Bulk machiningproduces devices with far greater mass but it is a much more expensivetechnology. Allied Signal produces bulk machined inertial sensors. Theadvantage of surface machining is the low cost and the ease ofincorporating the electronics close to the sensor.

[0016]FIG. 17 depicts the basis of the Charles Stark Draper Laboratorydesign based on an electronically-driven tuning fork method. The MEMSangular rate sensor measures angular rate voltage signals by picking-offa signal generated by an electromechanical oscillating mass as itdeviates from its plane of oscillation under the Coriolis force effectwhen submitted to a rotation about an axis perpendicular to the plane ofoscillation. Two vibrating proof masses are attached by springs to eachother and to the surrounding stationary material. The vibrating (dither)proof masses are driven in opposite directions by electrostatic combdrive motors to maintain lateral in-plane oscillation. The dither motionis in the plane of the wafer. When an angular rate is applied to theMEMS device about the input axis (which is in the plane of the tines),the proof masses are caused to oscillate out of plane by a Coriolisforce due to Coriolis effect. The resulting out-of-plane up and downoscillation motion amplitude, proportional to the input angular rate, isdetected and measured by capacitive pickoff plates underneath the proofmasses. The device can either be designed for closed loop or open loopoperation. Running the device closed loop adds more complexity but lesscross coupling and better linearity. The comb drives move the masses outof phase with respect to each other. The masses will then respond inopposite directions to the Corilois force.

[0017] Several MEMS accelerometers incorporate piezoresistive bridgessuch as those used in early micromechnical pressure gauges. Moreaccurate accelerometers are the force rebalance type that usesclosed-loop capacitive sensing and electrostatic forcing. Draper'smicromechnical accelerometer is a typical example, where theaccelerometer is a monolithic silicon structure consisting of atorsional pendulum with capacitive readout and electrostatic torquer.Analog Device's MEMS accelerometer has interdigitated ploysiliconcapacitive structure fabricated with on-chip BiMOS process to include aprecision voltage reference, local oscillators, amplifiers,demodulators, force rebalance loop and self-test functions.

[0018] Analog Device's MEMS accelerometer is a combination of springs,masses, motion sensing and actuation cells. It consists of a variabledifferential air capacitor whose plates are etched into the suspendedpolysilicon layer. The moving plate of the capacitor is formed by alarge number of “fingers” extending from the “beam”, a proof masssupported by tethers anchored to the substrate. Tethers provide themechanical spring constant that forces the proof mass to return to itsoriginal position when at rest or at constant velocity, as shown in FIG.18, which shows a micromachined sensor unit. The fixed plates of thecapacitor are formed by a number of matching pairs of fixed fingerspositioned on either side of the moving fingers attached to the beam,and anchored to the substrate.

[0019] When responding to an applied acceleration or under gravity, theproof mass' inertia causes it to move along a predetermined axis,relative to the rest of the chip, as shown in FIG. 19. As the fingersextending from the beam move between the fixed fingers, capacitancechange is being sensed and used to measure the amplitude of the forcethat led to the displacement of the beam.

[0020] To sense the change in capacitance between the fixed and movingplates, two 2 MHz square wave signals of equal amplitude but 180° out ofphase from each other, are applied to the fingers forming the fixedplates of the capacitor. At rest, the space between each one of thefixed plates and the moving plate is equidistant, and both signals arecoupled to the movable plate where they subtract from each otherresulting in a waveform of zero amplitude.

[0021] As soon as the chip experiences acceleration, the distancebetween one of the fixed plates and the movable plate increases whilethe distance between the other fixed plate and the movable platedecreases, resulting in capacitance imbalance. More of one of the twosquare wave signals gets coupled into the moving plate than the other,and the resulting signal at the output of the movable plate is a squarewave signal whose amplitude is proportional to the magnitude of theacceleration, and whose phase is indicative of the direction of theacceleration.

[0022] The signal is then fed into a buffer amplifier and further into aphase-sensitive demodulator (synchronized on the same oscillator thatgenerates the 1 MHz square wave excitation signals), which acts as afull wave-rectifier and low pass filter (with the use of an externalcapacitor). The output is a low frequency signal (dc to 1 kHzbandwidth), whose amplitude and polarity are proportional toacceleration and direction respectively. The synchronous demodulatordrives a preamplifier whose output is made available to the user.

[0023]FIG. 20 shows the silhouette of the sensor structure used inAnalog Device's MEMS accelerometer, ADXL 50. The microscopic sensorstructure is surrounded by signal conditioning circuitry on the samechip. The sensor has numerous fingers along each side of the movablecenter member; they constitute the center plates of a parallel set ofdifferential capacitors. Pairs of fixed fingers attached to thesubstrate interleave with the beam fingers to form the outer capacitorplates. The beam is supported by tethers, which serve as mechanicalsprings. The voltage on the moving plates is read via the electricallyconductive tether anchors that support the beam.

SUMMARY OF THE PRESENT INVENTION

[0024] A main objective of the present invention is to provide a methodof measuring motion, which successfully incorporates the MEMS technologywith the IMU industry.

[0025] Another objective of the present invention is to provide a methodof measuring motion which is adapted to be applied to output signals ofrate sensors and acceleration sensors, which are proportional torotation and translational motion of the carrier, respectively. Themethod of present invention is more suitable for emerging MEMS(MicroElectronicMechanicalSystem) rate and acceleration sensors.Compared with a conventional IMU, the present invention utilizes afeedforward open-loop signal processing scheme to obtain highly accuratemotion measurements by means of signal digitizing, temperature controland compensation, sensor error and misalignment calibrations, attitudeupdating, and damping controlling loops, and dramatically shrinks thesize of mechanical and electronic hardware and power consumption,meanwhile, obtains highly accurate motion measurements.

[0026] Another objective of the present invention is to provide a methodof measuring motion for outputting voltage signals of an angular rateproducer and an acceleration producer, such as an angular rate devicearray and acceleration device array, or an angular rate and accelerationsimulator are processed to obtain digital highly accurate digitalangular increment and velocity increment measurements of the carrier,and are further processed to obtain highly accurate attitude and headingmeasurements of the carrier under dynamic environments.

[0027] Although the present invention can be applicable to existingangular rate devices and acceleration devices, the present invention isspecifically suitable for emerging MEMS angular rate devices andacceleration devices assembled into a core micro IMU, wherein the coremicro IMU has the following unique features:

[0028] (1) Attitude Heading Reference System (AHRS) Capable Core SensorModule.

[0029] (2) Miniaturized (Length/Width/Height) and Light Weight.

[0030] (3) High Performance and Low Cost.

[0031] (4) Low Power Dissipation.

[0032] (5) Dramatic Improvement In Reliability (microelectromechanicalsystems—MEMS).

[0033] Another objective of the present invention is to provide a methodof measuring motion, which enables the core micro IMU rendering into anintegrated micro land navigator that has the following unique features:

[0034] (1) Miniature, light weight, low power, low cost.

[0035] (2) AHRS, odometer, integrated GPS chipset and flux valve.

[0036] (3) Integration filter for sensor data fusion and zero velocityupdating.

[0037] (4) Typical applications: automobiles, railway vehicles,miniature land vehicles, robots, unmanned ground vehicles, personalnavigators, and military land vehicles.

[0038] Another objective of the present invention is to provide a methodof measuring motion, which enables the core micro IMU to function asaircraft inertial avionics, which has the following unique features:

[0039] (1) Rate Gyro

[0040] (2) Vertical Gyro

[0041] (3) Directional Gyro

[0042] (4) AHRS

[0043] (5) IMU

[0044] (6) Inertial Navigation System

[0045] (7) Fully-Coupled GPS/MEMS IMU Integrated System

[0046] (8) Fully-Coupled GPS/IMU/Radar Altimeter Integrated System

[0047] (9) Universal vehicle navigation and control box.

[0048] Another objective of the present invention is to provide a methodof measuring motion, which enables the core micro IMU to function as aSpaceborne MEMS IMU Attitude Determination System and a SpaceborneFully-Coupled GPS/MEMS IMU Integrated system for orbit determination,attitude control, payload pointing, and formation flight, that have thefollowing unique features:

[0049] (1) Shock resistant and vibration tolerant

[0050] (2) High anti-jamming

[0051] (3) High dynamic performance

[0052] (4) Broad operating range of temperatures

[0053] (5) High resolution

[0054] (6) Compact, low power and light weight unit

[0055] (7) Flexible hardware and software architecture

[0056] Another objective of the present invention is to provide a methodof measuring motion which enables the core micro IMU to form a marineINS with embedded GPS, which has the following unique features:

[0057] (1) Micro MEMS IMU AHRS with Embedded GPS

[0058] (2) Built-in CDU (Control Display Unit)

[0059] (3) Optional DGPS (Differential GPS)

[0060] (4) Flexible Hardware and Software System Architecture

[0061] (5) Low Cost, Light Weight, High Reliability

[0062] Another objective of the present invention is to provide a methodof measuring motion which enables the core micro IMU to be used in amicro pointing and stabilization mechanism that has the following uniquefeatures:

[0063] (1) Micro MEMS IMU AHRS utilized for platform stabilization.

[0064] (2) MEMS IMU integrated with the electrical and mechanical designof the pointing and stabilization mechanism.

[0065] (3) Vehicle motion, vibration, and other interference rejected bya stabilized platform.

[0066] (4) Variable pointing angle for tracker implementations.

[0067] (5) Typical applications: miniature antenna pointing and trackingcontrol, laser beam pointing for optical communications, telescopicpointing for imaging, airborne laser pointing control for targeting,vehicle control and guidance.

BRIEF DESCRIPTION OF THE DRAWINGS

[0068]FIG. 1 is a block diagram illustrating the processing module forcarrier motion measurements according to a preferred embodiment of thepresent invention.

[0069]FIG. 2 is a block diagram illustrating the processing modules withthermal control processing for carrier motion measurements according tothe above preferred embodiment of the present invention.

[0070]FIG. 3 is a block diagram illustrating the processing modules withthermal compensation processing for carrier motion measurementsaccording to the above preferred embodiment of the present invention.

[0071]FIG. 4 is a block diagram illustrating an angular increment andvelocity increment producer for outputting voltage signals of angularrate producer and acceleration producer for carrier motion measurementsaccording to the above preferred embodiment of the present invention.

[0072]FIG. 5 is a block diagram illustrating another angular incrementand velocity increment producer for outputting voltage signals ofangular rate producer and acceleration producer for carrier motionmeasurements according to the above preferred embodiment of the presentinvention.

[0073]FIG. 6 is a block diagram illustrating another angular incrementand velocity increment producer for outputting voltage signals ofangular rate producer and acceleration producer for carrier motionmeasurements according to the above preferred embodiment of the presentinvention.

[0074]FIG. 7 is a block diagram illustrating another angular incrementand velocity increment producer for outputting voltage signals ofangular rate producer and acceleration producer for carrier motionmeasurements according to the above preferred embodiment of the presentinvention.

[0075]FIG. 8 is a block diagram illustrating a thermal processor foroutputting analog voltage signals of the thermal sensing produceraccording to the above preferred embodiment of the present invention.

[0076]FIG. 9 is a block diagram illustrating another thermal processorfor outputting analog voltage signals of the thermal sensing produceraccording to the above preferred embodiment of the present invention.

[0077]FIG. 10 is a block diagram illustrating another thermal processorfor outputting analog voltage signals of the thermal sensing produceraccording to the above preferred embodiment of the present invention.

[0078]FIG. 11 is a block diagram illustrating a processing module forcarrier motion measurements according to the above preferred embodimentof the present invention.

[0079]FIG. 12 is a block diagram illustrating a temperature digitizerfor outputting analog voltage signals of the thermal sensing produceraccording to the above preferred embodiment of the present invention.

[0080]FIG. 13 is a block diagram illustrating a temperature digitizerfor outputting analog voltage signals of the thermal sensing produceraccording to the above preferred embodiment of the present invention.

[0081]FIG. 14 is a block diagram illustrating a processing module withthermal compensation processing for carrier motion measurementsaccording to the above preferred embodiment of the present invention.

[0082]FIG. 15 is a block diagram illustrating the attitude and headingprocessing module according to the above preferred embodiment of thepresent invention.

[0083]FIG. 16 is a block diagram illustrating the MEMS tuning forkangular rate sensor principle.

[0084]FIG. 17 is a schematic view of a MEMS tuning fork angular ratesensor structure.

[0085]FIG. 18 is a schematic view of a micromachined sensor unit.

[0086]FIG. 19 is a schematic view of a sensor under an inputacceleration.

[0087]FIG. 20 is a schematic view of a silhouette plots of ADXL50.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENT

[0088] MEMS exploits the existing microelectronics infrastructure tocreate complex machines with micron feature sizes. These machines canhave many functions, including sensing, communication, and actuation.Extensive applications for these devices exist in a wide variety ofcommercial systems.

[0089] It is quite a straightforward idea that we can exploit the MEMSsensors' merits of small size, low cost, batch processing, and shockresistance to develop a low cost, light weight, miniaturized, highlyaccurate integrated MEMS motion measurement system.

[0090] It is well known that existing processing methods for motioninertial measurement unit are most suitable for conventional angularrate sensors or gyros and accelerometers, and can not produce optimalperformance for MEMS angular rate devices and acceleration devices.

[0091] The present invention provides a processing method for a motioninertial measurement unit, wherein output signals of angular rateproducer and acceleration producer, such as angular rate device arrayand acceleration device array, or an angular rate and accelerationsimulator, are processed to obtain highly accurate attitude and headingmeasurements of a carrier under dynamic environments.

[0092] The angular rate producer, such as MEMS angular rate device arrayor gyro array, provides three-axis angular rate measurement signals of acarrier. The acceleration producer, such as MEMS acceleration devicearray or accelerometer array, provides three-axis accelerationmeasurement signals of the carrier. The motion measurements of thecarrier, such as attitude and heading angles, achieved by means ofprocessing procedure of the three-axis angular rate measurement signalsfrom the angular rate producer and three-axis acceleration measurementsignals from the acceleration producer.

[0093] In the present invention, output signals of angular rate producerand acceleration producer are processed to obtain digital highlyaccurate angular rate increment and velocity increment measurements ofthe carrier and are further processed to obtain highly accurate attitudeand heading measurements of the carrier under dynamic environments. Thepresent invention is specifically suitable for emerging MEMS angularrate devices and acceleration devices, which are assembled into aninertial measurement unit (IMU), such as core micro IMU.

[0094] Referring to FIG. 1, the processing method for carrier motionmeasurement of the present invention comprises the following steps.

[0095] 1. Produce three-axis angular rate signals by an angular rateproducer 5 and three-axis acceleration signals by an accelerationproducer 10.

[0096] 2. Convert the three-axis angular rate signals into digitalangular increments and convert the input three-axis acceleration signalsinto digital velocity increments in an angular increment and velocityincrement producer 6.

[0097] 3. Compute attitude and heading angle measurements using thethree-axis digital angular increments and three-axis velocity incrementsin an attitude and heading processor 80.

[0098] In general, the angular rate producer 5 and the accelerationproducer 10 are very sensitive to a variety of temperature environments.In order to improve measurement accuracy, referring to FIG. 2, thepresent invention further comprises an additional thermal controllingloop step 4, processed in parallel with the above steps 1 to 3, ofmaintaining a predetermined operating temperature throughout the abovesteps, wherein the predetermined operating temperature is a constantdesignated temperature selected between 150° F. and 185° F., preferable176° F. (±1° F.).

[0099] The above thermal controlling loop step 4, as shown in FIG. 2,further comprises the steps of:

[0100] 4A-1. producing temperature signals by a thermal sensing producer15;

[0101] 4A-2. inputting the temperature signals to a thermal processor 30for computing temperature control commands using the temperaturesignals, a temperature scale factor, and a predetermined operatingtemperature of the angular rate producer 5 and the acceleration producer10;

[0102] 4A-3. producing driving signals to a heater device 20 using thetemperature control commands; and

[0103] 4A-4. outputting the driving signals to the heater device 20 forcontrolling the heater device 20 to provide adequate heat formaintaining the predetermined operating temperature throughout the abovesteps 1 to 3.

[0104] Temperature characteristic parameters of the angular rateproducer 5 and the acceleration producer 10 can be determined during aseries of the angular rate producer and acceleration producertemperature characteristic calibrations.

[0105] Referring to FIG. 3, when the above temperature controlling loopstep 4 is not provided, in order to compensate the angular rate producerand acceleration producer measurement errors induced by a variety oftemperature environments, after the above step 3, the present inventionfurther comprises the steps of:

[0106] 3A-1 producing temperature signals by a thermal sensing producer15 and outputting a digital temperature value to an attitude and headingprocessor 80 by means of a temperature digitizer 18;

[0107] 3A-2 accessing temperature characteristic parameters of theangular rate producer and the acceleration producer using a currenttemperature of the angular rate producer and the acceleration producerfrom the temperature digitizer 18; and

[0108] 3A-3 compensating the errors induced by thermal effects in theinput digital angular and velocity increments and computing attitude andheading angle measurements using the three-axis digital angularincrements and three-axis velocity increments in the attitude andheading processor 80.

[0109] In preferable applications, in the above step 1, the angular rateproducer 5 and the acceleration producer 10 are preferable MEMS angularrate device array and acceleration device array and the outputtingsignals of the angular rate producer 5 and the acceleration producer 10are analog voltage signals. Current MEMS rate and acceleration sensorsemploy an input reference voltage to generate an output voltage whichare proportional to input voltage and rotational and translationalmotion of a carrier, respectively. Therefore, step 1 further comprisesthe step of:

[0110] 1.1 acquiring three-axis analog angular rate voltage signals fromthe angular producer 5, which are directly proportional to carrierangular rates, and

[0111] 1.2 acquiring three-axis analog acceleration voltage signals fromthe acceleration producer 10, which are directly proportional to carrieraccelerations.

[0112] When the outputting analog voltage signals of angular rateproducer 5 and the acceleration producer 10 are too weak for the abovementioned integrating step 2 to read, the above producing step 1 prefersto further comprise amplifying steps 1.3 and 1.4 as follows after thestep 1.2 for amplifying the analog voltage signals input from theangular rate producer 5 and the acceleration producer 10 and suppressingnoise signals residing within the analog voltage signals input from theangular rate producer 5 and the acceleration producer 10, as shown inFIGS. 5 and 11.

[0113] 1.3 Amplify the three-axis analog angular rate voltage signalsand the three-axis analog acceleration voltage signals by means of afirst amplifier circuit 61 and a second amplifier circuit 67respectively to form amplified three-axis analog angular rate signalsand amplified three-axis analog acceleration signals respectively.

[0114] 1.4 Output the amplified three-axis analog angular rate signalsand the amplified three-axis analog acceleration signals to anintegrator circuit 62 and an integrator circuit 68.

[0115] Accordingly, referring to FIG. 4, the above converting step 2further comprises the following steps:

[0116] 2.1. Integrate the three-axis analog angular rate voltage signalsand the three-axis analog acceleration voltage signals for apredetermined time interval to accumulate the three-axis analog angularrate voltage signals and the three-axis analog acceleration voltagesignals as a raw three-axis angular increment and a raw three-axisvelocity increment for the predetermined time interval to achieveaccumulated angular increments and accumulated velocity increments. Theintegration is performed to remove noise signals that are non-directlyproportional to the carrier angular rate and acceleration within thethree-axis analog angular rate voltage signals and the three-axis analogacceleration voltage signals, to improve signal-to-noise ratio, and toremove the high frequency signals in the three-axis analog angular ratevoltage signals and the three-axis analog acceleration voltage signals.The signals that are directly proportional to the carrier angular rateand acceleration within the three-axis analog angular rate voltagesignals and the three-axis analog acceleration voltage signals can beused in subsequent processing steps.

[0117] 2.2 Form an angular reset voltage pulse and a velocity resetvoltage pulse as an angular scale and a velocity scale respectively.

[0118] 2.3 Measure the voltage values of the three-axis accumulatedangular increments and the three-axis accumulated velocity incrementswith the angular reset voltage pulse and the velocity reset voltagepulse respectively to acquire angular increment counts and velocityincrement counts as a digital form of angular and velocity measurementsrespectively.

[0119] In order to output real three-angular increment and velocityincrement values as an optional output format to substitute the voltagevalues of the three-axis accumulated angular increments and velocityincrements, after the above step 2.3 the converting step 2 furthercomprises an additional step of:

[0120] 2.4 scaling the voltage values of the three-axis accumulatedangular and velocity increments into real three-axis angular andvelocity increment voltage values.

[0121] In the integrating step 2.1, the three-axis analog angularvoltage signals and the three-axis analog acceleration voltage signalsare each reset to accumulate from a zero value at an initial point ofevery predetermined time interval.

[0122] Moreover, in general, the angular reset voltage pulse and thevelocity reset voltage pulse in the step 2.2 may be implemented byproducing a timing pulse by an oscillator 66, as shown in FIG. 6.

[0123] In the step 2.3, the measurement of the voltage values of thethree-axis accumulated angular and velocity increments can beimplemented by an analog/digital converter 650, as shown in FIG. 7. Inother words, step 2.3 is substantially a digitization step fordigitizing the raw three-axis angular and velocity increment voltagevalues into digital three-axis angular and velocity increments.

[0124] In applications, the above amplifying, integrating,analog/digital converter 650 and oscillator 66 can be built withcircuits, such as Application Specific Integrated Circuits(ASIC) chipand a printed circuit board.

[0125] As shown in FIG. 11, the step 2.3 further comprises the steps of:

[0126] 2.3.1 inputting the accumulated angular increments and theaccumulated velocity increments into an angular analog/digital converter63 and a velocity analog/digital converter 69 respectively;

[0127] 2.3.2 digitizing the accumulated angular increments by theangular analog/digital converter 63 by measuring the accumulated angularincrements with the angular reset voltage pulse to form a digitalangular measurements of voltage in terms of the angular increment countswhich is output to an input/output interface circuit 65;

[0128] 2.3.3 digitizing the accumulated velocity increments by thevelocity analog/digital converter 69 by measuring the accumulatedvelocity increments with the velocity reset voltage pulse to form adigital velocity measurements of voltage in terms of the velocityincrement counts which is output to an input/output interface circuit65; and

[0129] 2.3.4 outputting the digital three-axis angular and velocityincrement voltage values by the input/output interface circuit 65.

[0130] In order to achieve flexible adjustment of the thermal processor30 for a thermal sensing producer 15 with analog voltage output and aheater device 20 with analog input, thermal processor 30 can beimplemented in a digital feedback controlling loop as shown in FIG. 8.Referring to FIG. 8, the above thermal controlling loop step 4alternatively comprises the steps of:

[0131] 4B-1 producing temperature voltage signals by a thermal sensingproducer 15 to an analog/digital converter 304.

[0132] 4B-2 sampling the temperature voltage signals in theanalog/digital converter 304 and digitizing the sampled temperaturevoltage signals to digital signals which are output to the temperaturecontroller 306.

[0133] 4B-3 computing digital temperature commands in a temperaturecontroller 306 using the input digital signals from the analog/digitalconverter 304, a temperature sensor scale factor, and a pre-determinedoperating temperature of the angular rate producer and accelerationproducer, wherein the digital temperature commands are fed back to adigital/analog converter 303, and

[0134] 4B-4 converting the digital temperature commands input from thetemperature controller 306 in the digital/analog converter 303 intoanalog signals which are output to a heater device 20 to provideadequate heat for maintaining the predetermined operating temperaturethroughout the above steps 1 to 3.

[0135] If the voltage signals produced by the thermal sensing producer15 are too weak for the analog/digital converter 304 to read, referringto FIG. 9 there is an additional amplifying step 4-0 processed betweenthe thermal sensing producer 15 and the digital/analog converter 303.

[0136] The amplifying step 4-0: Acquire voltage signals from the thermalsensing producer 15 to a first amplifier circuit 301 for amplifying thesignals and suppressing the noise residing in the voltage signals andimproving the signal-to-noise ratio, wherein the amplified voltagesignals are output to the analog/digital converter 304.

[0137] Generally, the heater device 20 requires a specific drivingcurrent signals. In this case, referring to FIG. 10, there is anamplifying step 4.5 preferred to be processed between the digital/analogconverter 303 and heater device 20:

[0138] Step 4B-5: amplifying the input analog signals from thedigital/analog converter 303 for driving the heater device 20 in asecond amplifier circuit 302; and closing the temperature controllingloop.

[0139] Sequentially, as shown in FIG. 10, the step 4B-4 furthercomprises the step of:

[0140] 4B-4A converting the digital temperature commands input from thetemperature controller 306 in the digital/analog converter 303 intoanalog signals which are output to the amplifier circuit 302.

[0141] Sometimes, an input/output interface circuit 305 is required toconnect the analog/digital converter 304 and digital/analog converter303 and with the temperature controller 306. In this case, referring toFIG. 11, the step 4B-2 comprises the step of:

[0142] 4B-2A sampling the voltage signals in the analog/digitalconverter 304 and digitizing the sampled voltage signals, and thedigital signals are output to the input/output interface circuit 305.

[0143] Sequentially, as shown in FIG. 11, the step 4B-3 comprises thestep of:

[0144] 4B-3A computing digital temperature commands in the temperaturecontroller 306 using the input digital temperature voltage signals fromthe input/output interface circuit 305, the temperature sensor scalefactor, and the pre-determined operating temperature of the angular rateproducer and acceleration producer, wherein the digital temperaturecommands are fed back to the input/output interface circuit 305.

[0145] Moreover, as shown in FIG. 11, the step 4B-4 further comprisesthe step of:

[0146] 4B-4B converting the digital temperature commands input from theinput/output interface circuit 305 in the digital/analog converter 303into analog signals which are output to the heater device 20 to provideadequate heat for maintaining the predetermined operating temperaturethroughout the above steps 1 to 3.

[0147] Referring to FIG. 12, the above mentioned step 3A-1 can beimplemented by an analog/digital converter 182 for the thermal sensingproducer 15 with analog voltage output. If the voltage signals producedby the thermal sensing producer 15 are too weak for the analog /digitalconverter 182 to read, referring to FIG. 13, there is an additionalamplifying step processed between the thermal sensing producer 15 andthe digital/analog converter 182. The step 3A-1 further comprises thesteps of:

[0148] 3A-1.1 acquiring voltage signals from the thermal sensingproducer 15 to the amplifier circuit 181 for amplifying the signals andsuppressing the noise residing in the voltage signals and improving thevoltage signal-to-noise ratio, wherein the amplified voltage signals areoutput to the analog/digital converter 182, and

[0149] 3A-1.2 sampling the input amplified voltage signals in theanalog/digital converters 182 and digitizing the sampled voltage signalsto form digital signals outputting to the attitude and heading processor80.

[0150] Sometimes, an input/output interface circuit 183 is required toconnect the analog/digital converter 182 with the attitude and headingprocessor 80. In this case, referring to FIG. 14, the step 3A-1.2comprises the step of:

[0151] 3A-1.2A sampling the input amplified voltage signals in theanalog/digital converters 182 and digitizing the sampled voltage signalsto form digital signals outputting to the input/output interface circuit183.

[0152] Referring to FIG. 1, the digital three-axis angular incrementvoltage values or real values and three-axis digital velocity incrementvoltage values or real values are produced and outputted by the step 2.

[0153] In order to adapt to digital three-axis angular increment voltagevalue and three-axis digital velocity increment voltage values from thestep 2, referring to FIG. 15, the above mentioned step 3 furthercomprises the steps of:

[0154] 3B.1 inputting digital three-axis angular increment voltagevalues from the input/output interface circuit 65 of the step 2 andcoarse angular rate bias obtained from an angular rate producer andacceleration producer calibration procedure in high data rate (shortinterval) into a coning correction module 801; computing coning effecterrors in the coning correction module 801 using the input digitalthree-axis angular increment voltage values and coarse angular ratebias; and outputting three-axis coning effect terms and three-axisangular increment voltage values at reduced data rate (long interval),which are called three-axis long-interval angular increment voltagevalues, into a angular rate compensation module 802,

[0155] 3B.2 inputting the coning effect errors and three-axislong-interval angular increment voltage values from the coningcorrection module 801 and angular rate device misalignment parameters,fine angular rate bias, angular rate device scale factor, and coningcorrection scale factor from the angular rate producer and accelerationproducer calibration procedure to the angular rate compensation module802; compensating definite errors in the input three-axis long-intervalangular increment voltage values using the input coning effect errors,angular rate device misalignment parameters, fine angular rate bias, andconing correction scale factor; transforming the compensated three-axislong-interval angular increment voltage values to real three-axislong-interval angular increments using the angular rate device scalefactor; and outputting the real three-axis angular increments to analignment rotation vector computation module 805,

[0156] 3B.3 inputting the three-axis velocity increment voltage valuesfrom the input/output interface circuit 65 of the step 2 andacceleration device misalignment, acceleration device bias, andacceleration device scale factor from the angular rate producer andacceleration producer calibration procedure to accelerometercompensation module 803; transforming the input three-axis velocityincrements voltage values into real three-axis velocity increments usingthe acceleration device scale factor; compensating the definite errorsin three-axis velocity increments using the input acceleration devicemisalignment, accelerometer bias; outputting the compensated three-axisvelocity increments to the level acceleration computation module 804,

[0157] 3B.4 updating a quaternion, which is a vector representingrotation motion of the carrier, using the compensated three-axis angularincrements from the angular rate compensation module 802, an eastdamping rate increment from an east damping computation module 808, anorth damping rate increment from a north damping computation module809, and vertical damping rate increment from a vertical dampingcomputation module 810; and the updated quaternion is output to adirection cosine matrix computation module 806,

[0158] 3B.5 computing the direction cosine matrix, using the inputupdated quaternion; and the computed direction cosine matrix is outputto a level acceleration computation module 804 and an attitude andheading angle extract module 807,

[0159] 3B.6 extracting attitude and heading angle using the directioncosine matrix from the direction cosine matrix computation module 806;outputting the heading angle into a vertical damping rate computationmodule 808,

[0160] 3B.7 computing level velocity increments using the inputcompensated three-axis velocity increments from the accelerationcompensation module 804 and the direction cosine matrix from thedirection cosine matrix computation module 806; outputting the levelvelocity increments to an east damping rate computation module 810 andnorth damping rate computation module 809,

[0161] 3B.8 computing east damping rate increments using the northvelocity increment of the input level velocity increments from the levelacceleration computation module 804; feeding back the east damping rateincrements to the alignment rotation vector computation module 805,

[0162] 3B.9 computing north damping rate increments using the eastvelocity increment of the input level velocity increments from the levelacceleration computation module 804; feeding back the north damping rateincrements to the alignment rotation vector computation module 805, and

[0163] 3B.10 computing vertical damping rate increments using thecomputed heading angle from the attitude and heading angle extractmodule 807 and a measured heading angle from an external sensor 90; andfeeding back the vertical damping rate increments to the alignmentrotation vector computation module 805.

[0164] In order to adapt to real digital three-axis angular incrementvalues and real three-axis digital velocity increment values from step2, referring to FIG. 15, the above mentioned step 3B.1˜3B.3 are modifiedinto:

[0165] 3B.1A inputting real digital three-axis angular increment valuesfrom the step 2 and coarse angular rate bias obtained from an angularrate producer and acceleration producer calibration procedure in highdata rate (short interval) into a coning correction module 801;computing coning effect errors in the coning correction module 801 usingthe input digital three-axis angular increment values and coarse angularrate bias; and outputting three-axis coning effect terms and three-axisangular increment values at reduced data rate (long interval), which arecalled three-axis long-interval angular increment values, into a angularrate compensation module 802,

[0166] 3B.2A inputting the coning effect errors and three-axislong-interval angular increment values from the coning correction module801 and angular rate device misalignment parameters and fine angularrate bias from the angular rate producer and acceleration producercalibration procedure to the angular rate compensation module 802;compensating definite errors in the input three-axis long-intervalangular increment values using the input coning effect errors, angularrate device misalignment parameters, fine angular rate bias, and coningcorrection scale factor; and outputting the real three-axis angularincrements to an alignment rotation vector computation module 805, and

[0167] 3B.3A inputting the three-axis velocity increment values fromStep 2 and acceleration device misalignment, and acceleration devicebias from the angular rate producer and acceleration producercalibration procedure to accelerometer compensation module 803;compensating the definite errors in three-axis velocity increments usingthe input acceleration device misalignment, accelerometer bias;outputting the compensated three-axis velocity increments to the levelacceleration computation module 804.

[0168] Referring to FIGS. 3, 14, and 15, which use temperaturecompensation method, in order to adapt to digital three-axis angularincrement voltage value and three-axis digital velocity incrementvoltage values from step 2, the above mentioned step 3A-2 furthercomprises the steps of:

[0169] 3A-2.1 inputting digital three-axis angular increment voltagevalues from the input/output interface circuit 65 of the step 2 andcoarse angular rate bias obtained from an angular rate producer andacceleration producer calibration procedure in high data rate (shortinterval) into a coning correction module 801; computing coning effecterrors in the coning correction module 801 using the input digitalthree-axis angular increment voltage values and coarse angular ratebias; and outputting three-axis coning effect terms and three-axisangular increment voltage values in reduced data rate (long interval),which are called three-axis long-interval angular increment voltagevalues, into a angular rate compensation module 802,

[0170] 3A-2.2 inputting the coning effect errors and three-axislong-interval angular increment voltage values from the coningcorrection module 801 and angular rate device misalignment parameters,fine angular rate bias, angular rate device scale factor, and coningcorrection scale factor from the angular rate producer and accelerationproducer calibration procedure to the angular rate compensation module802; inputting the digital temperature signals from input/outputinterface circuit 183 of the step 3A.1.2 and temperature sensor scalefactor; computing current temperature of angular rate producer;accessing angular rate producer temperature characteristic parametersusing the current temperature of angular rate producer; compensatingdefinite errors in the input three-axis long-interval angular incrementvoltage values using the input coning effect errors, angular rate devicemisalignment parameters, fine angular rate bias, and coning correctionscale factor; transforming the compensated three-axis long-intervalangular increment voltage values to real three-axis long-intervalangular increments; compensating temperature-induced errors in the realthree-axis long-interval angular increments using the angular rateproducer temperature characteristic parameters; and outputting the realthree-axis angular increments to an alignment rotation vectorcomputation module 805,

[0171] 3A-2.3 inputting the three-axis velocity increment voltage valuesfrom the input/output interface circuit 65 of the step 2 andacceleration device misalignment, acceleration bias, acceleration devicescale factor from the angular rate producer and acceleration producercalibration procedure to acceleration compensation module 803; inputtingthe digital temperature signals from input/output interface circuit 183of the step 3A-1 and temperature sensor scale factor; computing currenttemperature of acceleration producer; accessing acceleration producertemperature characteristic parameters using the current temperature ofacceleration producer; transforming the input three-axis velocityincrements voltage values into real three-axis velocity increments usingthe acceleration device scale factor; compensating the definite errorsin three-axis velocity increments using the input acceleration devicemisalignment, acceleration bias; compensating temperature-induced errorsin the real three-axis velocity increments using the accelerationproducer temperature characteristic parameters; and outputting thecompensated three-axis velocity increments to the level accelerationcomputation module 804,

[0172] 3A-2.4 updating a quaternion, which is a vector representingrotation motion of the carrier, using the compensated three-axis angularincrements from the angular rate compensation module 802, an eastdamping rate increment from an east damping computation module 808, anorth damping rate increment from a north damping computation module809, and vertical damping rate increment from a vertical dampingcomputation module 810; and the updated quaternion is output to adirection cosine matrix computation module 806,

[0173] 3A-2.5 computing the direction cosine matrix, using the inputupdated quaternion; and the computed direction cosine matrix is outputto a level acceleration computation module 804 and an attitude andheading angle extract module 807,

[0174] 3A-2.6 extracting attitude and heading angle using the directioncosine matrix from the direction cosine matrix computation module 806;outputting the heading angle into a vertical damping rate computationmodule 808,

[0175] 3A-2.7 computing level velocity increments using the inputcompensated three-axis velocity increments from the accelerationcompensation module 804 and the direction cosine matrix from thedirection cosine matrix computation module 806; outputting the levelvelocity increments to an east damping rate computation module 810 andnorth damping rate computation module 809,

[0176] 3A-2.8 computing east damping rate increments using the northvelocity increment of the input level velocity increments from the levelacceleration computation module 804, feeding back the east damping rateincrements to the alignment rotation vector computation module 805,

[0177] 3A-2.9 computing north damping rate increments using the eastvelocity increment of the input level velocity increments from the levelacceleration computation module 804; feeding back the north damping rateincrements to the alignment rotation vector computation module 805, and

[0178] 3A-2.10 computing vertical damping rate increments using thecomputed heading angle from the attitude and heading angel extractmodule 807 and a measured heading angle from an external sensor 90; andfeeding back the vertical damping rate increments to the alignmentrotation vector computation module 805.

[0179] Referring to FIGS. 3, 14, and 15, which use temperaturecompensation method, in order to adapt to real digital three-axisangular increment values and real three-axis digital velocity incrementvalues from the step 2, the above mentioned step 3A-2.1 are modifiedinto:

[0180] 3A-2.1A inputting digital three-axis angular increment valuesfrom the input/output interface circuit 65 of Step 2 and coarse angularrate bias obtained from an angular rate producer and accelerationproducer calibration procedure in high data rate (short interval) into aconing correction module 801; computing coning effect errors in theconing correction module 801 using the input digital three-axis angularincrement values and coarse angular rate bias; and outputting three-axisconing effect terms and three-axis angular increment values in reduceddata rate (long interval), which are called three-axis long-intervalangular increment values, into a angular rate compensation module 802,

[0181] 3A-2.2A inputting the coning effect errors and three-axislong-interval angular increment values from the coning correction module801 and angular rate device misalignment parameters and fine angularrate bias from the angular rate producer and acceleration producercalibration procedure to the angular rate compensation module 802;inputting the digital temperature signals from input/output interfacecircuit 183 of the step 3A-1.2 and temperature sensor scale factor;computing current temperature of angular rate producer; accessingangular rate producer temperature characteristic parameters using thecurrent temperature of angular rate producer; compensating definiteerrors in the input three-axis long-interval angular increment valuesusing the input coning effect errors, angular rate device misalignmentparameters, fine angular rate bias, and coning correction scale factor;compensating temperature-induced errors in the real three-axislong-interval angular increments using the angular rate producertemperature characteristic parameters; and outputting the realthree-axis angular increments to an alignment rotation vectorcomputation module 805, and

[0182] 3A-2.3A inputting the three-axis velocity increment values fromthe input/output interface circuit 65 of the step 2 and accelerationdevice misalignment and acceleration bias from the angular rate producerand acceleration producer calibration procedure to accelerationcompensation module 803; inputting the digital temperature signals frominput/output interface circuit 183 of the step 3A-1 and temperaturesensor scale factor; computing current temperature of accelerationproducer; accessing acceleration producer temperature characteristicparameters using the current temperature of acceleration producer;compensating the definite errors in three-axis velocity increments usingthe input acceleration device misalignment, acceleration bias;compensating temperature-induced errors in the real three-axis velocityincrements using the acceleration producer temperature characteristicparameters; and outputting the compensated three-axis velocityincrements to the level acceleration computation module 804.

[0183] In order to meet the diverse requirements of application systems,referring to FIGS. 11 and 14, an additional processing step, which isperformed after the above embodied step 2.3.1˜2.3.3, comprises:

[0184] Packing the digital three-axis angular increment voltage values,the digital three-axis velocity increment, and digital temperaturesignals in the input/output interface circuit 65 and the input/outputinterface circuit 305 with a specific format required by a external usersystem to use them, such as RS-232 serial communication standard, RS-422serial communication standard, popular PCI/ISA bus standard, and 1553bus standard, etc.

[0185] In order to meet diverse requirements of application systems, anadditional processing step, referring to FIGS. 1, 11 and 14, which isperformed after the above embodied step 3, comprises:

[0186] Packing the digital three-axis angular increment values, thedigital three-axis velocity increment, and obtained attitude and headingdata in the input/output interface circuit 85 with a specific formatrequired by a external user system to use them, such as RS-232 serialcommunication standard, RS-422 serial communication standard, PCI/ISAbus standard, and 1553 bus standard, etc.

[0187] Referring to FIG. 2, an alternative to the preferable thermalcontrol processing is disclosed as follows:

[0188] The first and second temperature sensors are used as the thermalsensing producer 15.

[0189] The first and second heaters are used as heater device 20.

[0190] The thermal processor 30 forms the first HTR (heater) loop forthe first temperature sensor and first heater and the second HTR(heater) loop for the second temperature sensor and second heater toimplement the thermal control to maintain the operational environment ofthe angular rate producer 5, acceleration producer 10, and the angularincrement and velocity increment producer for high quality performance.

[0191] Moreover, the preferred embodiment of the thermal controlcomputation tasks running in the thermal processor 30 comprises:

[0192] (a) performing parameter setting at turn on by initializing thefirst and second temperature constants of the first heater 1 and thesecond heater 2 to a value of 1 deg centigrade greater than the finaldestination temperature, respectively;

[0193] and for each new temperature data frame from the first and secondtemperature sensors, in an iterative fashion:

[0194] (b) adding the first temperature constant to the firsttemperature sensor value from the first temperature sensor and addingthe first result of the last frame value of the first heater loop toform the current first result;

[0195] (c) loading the current first result into the first down counterused to form the length of the first pulse which varies from 0 to 100%,wherein the first pulse is used to drive the first heater;

[0196] (d) saving the current first result for use during the nextiteration of the first heater loop;

[0197] (e) adding the second temperature constant to the secondtemperature sensor value from the second temperature sensor and addingthe second result of the last frame value of the second heater loop toform the current second result;

[0198] (f) loading the current second result into the second downcounter used to form the length of the second pulse which varies from 0to 100%, wherein the second pulse is used to drive the second heater;

[0199] (g) saving the current second result for use during the nextiteration of the second heater loop;

[0200] (h) setting the first temperature constant of the first heaterloop 1 to the final destination temperature and setting the secondheater loop 2 to off, when the temperature, which is the initially setat a value of 1 deg centigrade greater than the final destinationtemperature, is reached, as measured by both temperature sensors;

[0201] (i) setting the second temperature constant of heater loop 2 tothe value of second temperature sensor 2, and setting the second heaterloop 2 on, when the temperature cools to the final temperature, asmeasured by temperature sensor 1.

What is claimed is:
 1. A method for measuring motion of a user,comprising the steps of: (a) producing three-axis angular rate signalsby an angular rate producer and three-axis acceleration signals by anacceleration producer; (b) converting said three-axis angular ratesignals into digital angular increments and converting said inputthree-axis acceleration signals into digital velocity increments in anangular increment and velocity increment producer 6; and (c) computingattitude and heading angle measurements using said three-axis digitalangular increments and said three-axis velocity increments in anattitude and heading processor. (d) maintaining a predeterminedoperating temperature throughout said above steps, wherein saidpredetermined operating temperature is a constant designated temperatureselected between 150° F. and 185° F., by means of: (d.1) performingparameter setting at turn on by initializing first and secondtemperature constants of first heater and second heater to a value of 1deg centigrade greater than final destination temperature, respectively;and for each new temperature data frame from said first and secondtemperature sensors, in an iterative fashion: (d.2) adding said firsttemperature constant to said first temperature sensor value from saidfirst temperature sensor and adding said first result of said last framevalue of said first heater loop to form said current first result; (d.3)loading said current first result into said first down counter used toform said length of said first pulse which varies from 0 to 100%,wherein said first pulse is used to drive said first heater; (d.4)saving said current first result for use during said next iteration ofsaid first heater loop; (d.5) adding said second temperature constant tosaid second temperature sensor value from said second temperature sensorand adding said second result of said last frame value of said secondheater loop to form said current second result; (d.6) loading saidcurrent second result into said second down counter used to form saidlength of said second pulse which varies from 0 to 100%, wherein saidsecond pulse is used to drive said second heater; (d.7) saving saidcurrent second result for use during said next iteration of said secondheater loop; (d.8) setting said first temperature constant of said firstheater loop to said final destination temperature and setting saidsecond heater loop to off, when said temperature, which is saidinitially set at a value of 1 deg centigrade greater than said finaldestination temperature, is reached, as measured by both temperaturesensors; (d.9) setting said second temperature constant of heater loopto said value of second temperature sensor 2, and setting said secondheater loop on, when said temperature cools to said final temperature,as measured by temperature sensor.
 2. The method for measuring motion ofa user, as recited in claim 1 , wherein said angular rate producer andsaid acceleration producer are MEMS angular rate device
 3. The methodfor measuring motion of a user, as recited in claim 2 , wherein saidstep (a) further comprises said steps of: (a.1) acquiring three-axisanalog angular rate voltage signals from said angular producer, whichare directly proportional to carrier angular rates, and (a.2) acquiringthree-axis analog acceleration voltage signals from said accelerationproducer, which are directly proportional to carrier accelerations. 4.The method for measuring motion of a user, as recited in claim 3 ,wherein said step (a) further comprises amplifying steps of amplifyingsaid analog voltage signals input from said angular rate producer andsaid acceleration producer and suppressing noise signals residing withinsaid analog voltage signals input from said angular rate producer andsaid acceleration producer.
 5. The method for measuring motion of auser, as recited in claim 4 , wherein said amplifying step comprisessaid steps of: (a.3) amplifying said three-axis analog angular ratevoltage signals and said three-axis analog acceleration voltage signalsby means of a first amplifier circuit and a second amplifier circuitrespectively to form amplified three-axis analog angular rate signalsand amplified three-axis analog acceleration signals respectively; and(a.4) outputting said amplified three-axis analog angular rate signalsand said amplified three-axis analog acceleration signals to anintegrator circuit and an integrator circuit,
 6. The method formeasuring motion of a user, as recited in claim 5 , wherein said step(b) further comprises said steps of: (b.1) integrating said three-axisanalog angular rate voltage signals and said three-axis analogacceleration voltage signals for a predetermined time interval toaccumulate said three-axis analog angular rate voltage signals and saidthree-axis analog acceleration voltage signals as a raw three-axisangular increment and a raw three-axis velocity increment for saidpredetermined time interval to achieve accumulated angular incrementsand accumulated velocity increments, for removing noise signals that arenon-directly proportional to said carrier angular rate and accelerationwithin said three-axis analog angular rate voltage signals and saidthree-axis analog acceleration voltage signals, improvingsignal-to-noise ratio, and removing said high frequency signals in saidthree-axis analog angular rate voltage signals and said three-axisanalog acceleration voltage signals; (b.2) forming an angular resetvoltage pulse and a velocity reset voltage pulse as an angular scale anda velocity scale respectively; (b.3) measuring said voltage values ofsaid three-axis accumulated angular increments and said three-axisaccumulated velocity increments with said angular reset voltage pulseand said velocity reset voltage pulse respectively to acquire angularincrement counts and velocity increment counts as a digital form ofangular and velocity measurements respectively; and (b.4) scaling saidvoltage values of said three-axis accumulated angular and velocityincrements into real three-axis angular and velocity increment voltagevalues.
 7. The method for measuring motion of a user, as recited inclaim 6 , wherein in said step (b.1) said three-axis analog angularvoltage signals and said three-axis analog acceleration voltage signalsare each reset to accumulate from a zero value at an initial point ofevery predetermined time interval.
 8. The method for measuring motion ofa user, as recited in claim 6 , wherein in said step (b.2), said angularreset voltage pulse and said velocity reset voltage pulse areimplemented by producing a timing pulse by an oscillator.
 9. The methodfor measuring motion of a user, as recited in claim 6 , wherein in saidstep (b.3), said measurement of said voltage values of said three-axisaccumulated angular and velocity increments are implemented by ananalog/digital converter, for digitizing said raw three-axis angular andvelocity increment voltage values into digital three-axis angular andvelocity increments.
 10. The method for measuring motion of a user, asrecited in claim 6 , wherein said step (b.3) further comprises saidsteps of: (b.3.1) inputting said accumulated angular increments and saidaccumulated velocity increments into an angular analog/digital converterand a velocity analog/digital converter respectively; (b.3.2) digitizingsaid accumulated angular increments by said angular analog/digitalconverter by measuring said accumulated angular increments with saidangular reset voltage pulse to form a digital angular measurements ofvoltage in terms of said angular increment counts which is output to aninput/output interface circuit; (b.3.3) digitizing said accumulatedvelocity increments by said velocity analog/digital converter bymeasuring said accumulated velocity increments with said velocity resetvoltage pulse to form a digital velocity measurements of voltage interms of said velocity increment counts which is output to said aninput/output interface circuit; and (b.3.4) outputting said digitalthree-axis angular and velocity increment voltage values by saidinput/output interface circuit.
 11. The method for measuring motion of auser, as recited in claim 1 to 10, wherein in order to adapt to digitalthree-axis angular increment voltage value and three-axis digitalvelocity increment voltage values from said step (b), said step (c)further comprises said steps of: (cb.1) inputting digital three-axisangular increment voltage values from said input/output interfacecircuit of said step (b) and coarse angular rate bias obtained from anangular rate producer and acceleration producer calibration procedure inhigh data rate for a short interval into a coning correction module;computing coning effect errors in said coning correction module usingsaid input digital three-axis angular increment voltage values andcoarse angular rate bias; and outputting three-axis coning effect termsand three-axis angular increment voltage values at reduced data rate fora long interval, which are called three-axis long-interval angularincrement voltage values, into a angular rate compensation module,(cb.2) inputting said coning effect errors and three-axis long-intervalangular increment voltage values from said coning correction module andangular rate device misalignment parameters, fine angular rate bias,angular rate device scale factor, and coning correction scale factorfrom said angular rate producer and acceleration producer calibrationprocedure to said angular rate compensation module; compensatingdefinite errors in said input three-axis long-interval angular incrementvoltage values using said input coning effect errors, angular ratedevice misalignment parameters, fine angular rate bias, and coningcorrection scale factor; transforming said compensated three-axislong-interval angular increment voltage values to real three-axislong-interval angular increments using said angular rate device scalefactor; and outputting said real three-axis angular increments to analignment rotation vector computation module, (cb.3) inputting saidthree-axis velocity increment voltage values from said input/outputinterface circuit of said step (b) and acceleration device misalignment,acceleration device bias, and acceleration device scale factor from saidangular rate producer and acceleration producer calibration procedure toaccelerometer compensation module; transforming said input three-axisvelocity increments voltage values into real three-axis velocityincrements using said acceleration device scale factor; compensatingsaid definite errors in three-axis velocity increments using said inputacceleration device misalignment, accelerometer bias; outputting saidcompensated three-axis velocity increments to said level accelerationcomputation module, (cb.4) updating a quaternion, which is a vectorrepresenting rotation motion of said carrier, using said compensatedthree-axis angular increments from said angular rate compensationmodule, an east damping rate increment from an east damping computationmodule, a north damping rate increment from a north damping computationmodule, and vertical damping rate increment from a vertical dampingcomputation module; and said updated quaternion is output to a directioncosine matrix computation module, (cb.5) computing said direction cosinematrix, using said input updated quaternion; and said computed directioncosine matrix is output to a level acceleration computation module andan attitude and heading angle extract module, (cb.6) extracting attitudeand heading angle using said direction cosine matrix from said directioncosine matrix computation module; outputting said heading angle into avertical damping rate computation module, (cb.7) computing levelvelocity increments using said input compensated three-axis velocityincrements from said acceleration compensation module and said directioncosine matrix from said direction cosine matrix computation module;outputting said level velocity increments to an east damping ratecomputation module and north damping rate computation module, (cb.8)computing east damping rate increments using said north velocityincrement of said input level velocity increments from said levelacceleration computation module; feeding back said east damping rateincrements to said alignment rotation vector computation module, (cb.9)computing north damping rate increments using said east velocityincrement of said input level velocity increments from said levelacceleration computation module; feeding back said north damping rateincrements to said alignment rotation vector computation module, and(cb.10) computing vertical damping rate increments using said computedheading angle from said attitude and heading angle extract module and ameasured heading angle from an external sensor; and feeding back saidvertical damping rate increments to said alignment rotation vectorcomputation module.
 12. The method for measuring motion of a user, asrecited in claim 10 , wherein in order to adapt to real digitalthree-axis angular increment value and three-axis digital velocityincrement values from said step (b), said step (c) further comprisessaid steps of: (cb.1) inputting real digital three-axis angularincrement values from said step (b) and coarse angular rate biasobtained from an angular rate producer and acceleration producercalibration procedure in high data rate for a short interval into aconing correction module; computing coning effect errors in said coningcorrection module using said input digital three-axis angular incrementvalues and coarse angular rate bias; and outputting three-axis coningeffect terms and three-axis angular increment values at reduced datarate (long interval), which are called three-axis long-interval angularincrement values, into a angular rate compensation module, (cb.2)inputting said coning effect errors and three-axis long-interval angularincrement values from said coning correction module and angular ratedevice misalignment parameters and fine angular rate bias from saidangular rate producer and acceleration producer calibration procedure tosaid angular rate compensation module; compensating definite errors insaid input three-axis long-interval angular increment values using saidinput coning effect errors, angular rate device misalignment parameters,fine angular rate bias, and coning correction scale factor; andoutputting said real three-axis angular increments to an alignmentrotation vector computation module, (cb.3) inputting said realthree-axis velocity increment values from said step (b) and accelerationdevice misalignment, and acceleration device bias from said angular rateproducer and acceleration producer calibration procedure toaccelerometer compensation module; compensating said definite errors inthree-axis velocity increments using said input acceleration devicemisalignment, accelerometer bias; outputting said compensated three-axisvelocity increments to said level acceleration computation module,(cb.4) updating a quaternion, which is a vector representing rotationmotion of said carrier, using said compensated three-axis angularincrements from said angular rate compensation module, an east dampingrate increment from an east damping computation module, a north dampingrate increment from a north damping computation module, and verticaldamping rate increment from a vertical damping computation module; andsaid updated quaternion is output to a direction cosine matrixcomputation module, (cb.5) computing said direction cosine matrix, usingsaid input updated quaternion; and said computed direction cosine matrixis output to a level acceleration computation module and an attitude andheading angle extract module, (cb.6) extracting attitude and headingangle using said direction cosine matrix from said direction cosinematrix computation module; outputting said heading angle into a verticaldamping rate computation module, (cb.7) computing level velocityincrements using said input compensated three-axis velocity incrementsfrom said acceleration compensation module and said direction cosinematrix from said direction cosine matrix computation module; outputtingsaid level velocity increments to an east damping rate computationmodule and north damping rate computation module, (cb.8) computing eastdamping rate increments using said north velocity increment of saidinput level velocity increments from said level acceleration computationmodule; feeding back said east damping rate increments to said alignmentrotation vector computation module, (cb.9) computing north damping rateincrements using said east velocity increment of said input levelvelocity increments from said level acceleration computation module;feeding back said north damping rate increments to said alignmentrotation vector computation module, and (cb.10) computing verticaldamping rate increments using said computed heading angle from saidattitude and heading angle extract module and a measured heading anglefrom an external sensor; and feeding back said vertical damping rateincrements to said alignment rotation vector computation module.